In a large bowl, combine flour, salt, and ajwain to prepare the dough for samosa.
Add oil or ghee and rub it into the flour until it resembles breadcrumbs.
Gradually add water and knead into a firm dough. Don't add too much water otherwise it will soak oil.
Cover the samosa dough with a cloth and let it rest for 30 minutes.
Heat 2 tbsp oil in a pan, add cumin seeds and let them splutter.
Add ginger and green chili, sauté briefly.
Add green peas and cook for 1–2 minutes.
Stir in mashed potatoes, spices, and salt to make spicy samosa filling.
Cook for 2 minutes and finish with chopped coriander leaves. Let it cool.
Divide dough into small balls and roll each into an oval shape.
To shape the samosa, cut the oval in half to form two semi-circles.
Wet the straight edge, form a cone shape, and seal.
Fill the samosa with 1–2 tbsp filling but avoid overfilling the samosa, seal the top with water, and set aside.
Heat oil in a deep pan over medium-low heat.
Fry samosas in batches on medium heat until samosas turn golden and crispy.
Turn samosas occasionally to ensure even frying from all sides.
Remove samosas from oil and drain on paper towels.
Serve hot samosas with mint chutney, tamarind chutney, or ketchup.